Peyton Westlake is a scientist still searching for the key to creating a permanent liquid-skin formula to mend his burned face and body, and he continues to operate as the vigilante Darkman. He interrupts a dangerous exchange led by the power-hungry crime boss Peter Rooker, who becomes fascinated by Westlake’s superhuman strength and agility.
Westlake is soon approached by Dr. Bridget Thorne, one of the physicians who saved his life after the brutal attack that left him scarred years earlier. She offers to help him complete his liquid-skin formula, while also theorizing she can surgically repair his nervous system, restoring some of the sensory loss he has endured since the attack.
Together they travel to a laboratory that Thorne has set up in an abandoned industrial complex, where she performs the surgery and Westlake manages to create a small amount of permanent liquid skin that does not break down in sunlight the way his earlier samples did.
But trouble arrives when Peter Rooker shows up and reveals that Thorne is his mistress. He makes clear that he desires the enhanced strength that Westlake possesses and, with Thorne’s help, plans to use him as a guinea pig to replicate the perpetual adrenal overload that powers him. Thorne also confesses that she implanted an electrical shock-device into the back of Westlake’s neck to keep him under control. The duo steals Westlake’s skin sample and a computer disk containing his research, subjecting him to a brutal and exhaustive battery of tests. He finally finds a way to remove the neck device with a pair of pliers and escapes.
In the aftermath, Westlake encounters Rooker’s neglected wife Angela Rooker and their young daughter Jenny. At first, he is wary, but he soon sees how lonely and empty his own life has been, and a genuine bond begins to form. Using his extraordinary abilities, he projects himself into the life of a devoted husband and father, even accompanying Jenny to watch her school’s production of Beauty and the Beast.
Rooker, not finished, uses the data from Westlake’s tests to create a new super-strength formula and distributes it to his men, ordering them to assassinate a hopeful district attorney during a public gathering. Westlake arrives just in time to thwart the assassination. He then discovers that Westlake had stolen Rooker’s identity to spend time with his family, and in a shocking turn, Rooker murders Thorne and coldly declares that he plans to be a better husband and father to Angela.
Rooker drags his family back to Thorne’s lab and holds them hostage. Westlake tracks them down, only to learn that Rooker has injected himself with the last of the super-strength formula, which not only increases his power but seems to push him deeper into madness. A brutal showdown ensues across the lab, during which Westlake reclaim the permanent liquid skin sample but the research disk is destroyed. He finally gains the upper hand and tricks Rooker into falling into an industrial shredding machine, killing him.
A gas line in the building erupts into a massive fireball, and Westlake manages to rescue Angela and Jenny, though Jenny sustains severe facial burns. In a selfless decision, Westlake resolves to use the liquid skin to repair Jenny’s face rather than his own. Angela thanks him for saving her daughter, and he then departs to continue his work on the formula while vowing to keep fighting crime and injustice.
